PROJECT SUMMARY Childhood asthma and obesity are pressing health epidemics in the United States that disproportionately impact children who are minorities and come from households with lower incomes. Asthma in obese children tends to be more severe and refractory to treatment. An emerging explanatory hypothesis is that these children may be more vulnerable to components of air pollution. Secondhand smoke is a dominant source of indoor air pollution, particularly in the inner city, where up to 80% of children with asthma are regularly exposed. The differential effects of secondhand smoke based on weight are not known. We hypothesize that secondhand smoke is preferentially deleterious to overweight or obese children with asthma, and that this relationship may correlate with differences in inflammation and oxidative stress. Because obesity is associated with basal elevations in inflammation and because asthma is associated with enhanced inflammation and oxidative stress, we believe that this is a plausible biologic mechanism. We have discovered compelling preliminary evidence from the National Health and Nutrition Examination Survey (NHANES) that children who are overweight or obese report greater symptoms when exposed to secondhand smoke as compared to normal weight children. This project extends the results of this analysis to a local level, in more well-characterized cohorts of children who have both symptom and blood biomarker assessment. This study will be performed in (1) two large observational cohorts of children with asthma, comparing those who are and are not exposed to secondhand smoke, and in (2) an interventional cohort of children with asthma who are all exposed to secondhand smoke and have subsequent reductions in secondhand smoke exposure through the use of an advanced air purifier, comparing differences in asthma improvement between those who are normal weight and overweight or obese. As body mass index is an imperfect marker for adiposity, this project will also examine if other different measures of adiposity, waist circumference and percentage body fat as estimated by bioelectrical impedance analysis, perform better than body mass index in identifying this vulnerable group.